1. Field of the Invention
The present invention relates to a semiconductor device comprising a semiconductor chip encapsulated with a mold resin, and more particularly to a semiconductor device comprising a semiconductor chip generating a large quantity of heat, encapsulated with a mold resin.
2. Description of Related Art
Because a semiconductor chip is encapsulated with a mold resin (an encapsulating resin) in a semiconductor device, heat generated in the semiconductor chip readily resides within the semiconductor device (a mold resin). It is therefore necessary for a semiconductor device provided with a semiconductor chip that generates a large quantity of heat while it is driven to efficiently dissipate heat generated in the semiconductor chip to the outside of the semiconductor device.
For example, Japanese Unexamined Patent Publication No. 60-160639(1985) has disclosed a semiconductor device, in which a lead frame joined to one surface of the semiconductor chip is exposed through a mold resin in the vicinity of the joint to the semiconductor chip. With this semiconductor device, heat generated in the semiconductor chip is chiefly dissipated to the outside via the exposed portion of the lead frame through the mold resin.
Also, Japanese Unexamined Patent Publication No. 8-298302(1996) and Japanese Unexamined Patent Publication No. 10-321768(1998) have disclosed a semiconductor device, in which a heat-spreading plate or a heat-spreading body joined to one surface of the semiconductor chip instead of the lead frame is exposed to the outside of a mold resin. With this semiconductor device, heat generated in the semiconductor chip is chiefly dissipated to the outside via the exposed portion of the heat-spreading plate or heat-spreading body through the mold resin.
Further, there is known a semiconductor device, in which the semiconductor chip is directly exposed through the mold resin. This semiconductor device is shaped like a rectangular prism, and the semiconductor chip is exposed through the center of one surface of the semiconductor device. Heat generated in the semiconductor chip is thus directly dissipated to the outside of the semiconductor device. This semiconductor device is mounted on a wiring board in an orientation such that the surface from which the semiconductor chip is exposed opposes the wiring board.
In the case of the semiconductor chip generating a large quantity of heat, however, the semiconductor device having the structure described above is not able to dissipate heat generated in the semiconductor chip in a satisfactory manner, and there has been a need for a semiconductor device with an enhanced heat-spreading capability.
In addition, a semiconductor device in which the semiconductor chip is exposed directly through the mold resin has a problem that the semiconductor chip readily breaks. Further, in a case where the exposed semiconductor chip is joined to the wiring board through soldering or the like in such a semiconductor device, because the joint is hidden in a space between the semiconductor device and the wiring board, direct visual inspection of the joint is impossible, which makes it difficult to confirm whether the two components are joined to each other in a satisfactory manner.